The Dolphins have not decided on a starting running back for their regular-season opener in less than three weeks, and anyone doubting that merely has to monitor what the team is doing as well as saying.

The Dolphins have not decided on a starting running back for their regular-season opener in less than three weeks, and anyone doubting that merely has to monitor what the team is doing as well as saying.

Ask coach Joe Philbin if the starting job is open, and he interrupts the query before it reaches the question mark.

“Absolutely,” Philbin said Tuesday.

That answer came only minutes after the Dolphins finished their first regular-season-style practice in preparation for Saturday night’s dress rehearsal game in which starters will play into the second half against Tampa Bay at Sun Life Stadium.

And in this important practice leading up to this important exhibition game, running backs Lamar Miller and Daniel Thomas shared first-team snaps in 11-on-11 drills.

Miller, the presumed starter earlier in training camp, got nine snaps with the first team during Monday’s practice. Thomas, who has not started a game this preseason but is pushing for the starting job after a couple of solid outings, got 12 snaps with the starters.

Yes, this job is wide open.

So someone needs to, you know, actually step forward and take it because the longer it dangles the less certainty the Dolphins enjoy about what exactly they have in the backfield.

The longer the Dolphins go without picking a starting running back, the more it suggests neither Thomas nor Miller are ready to separate from the other or, worse, ready to be an NFL starter.

This wouldn’t be an issue if we were talking about Jim Kiick and Mercury Morris vying for the same starting job. No one would be worried if we were talking about veterans who have actually performed well in the NFL.

Instead we’re talking about two young, mostly unproven players.

Interestingly, the company line from the Dolphins is that neither Thomas nor Miller has snatched this grand opportunity but both are really, really good.

“If you have a No. 1 running back and a No. 2 that’s a distant 2 it’s probably not as good as a 1 and a 1A,” offensive coordinator Mike Sherman said. “I think we have a 1 and 1A so we have two really good ones, or have a chance to be.

“They’re both very young. They don’t have a lot of snaps in them just yet. But they both have a chance to be good running backs in this league and see how far they can go. I’d rather have two good ones than one, put it that way.”

That sounds convincing. But how does Sherman know? How can he be so sure that both Miller and Thomas are really good?

Well, he can’t. He’s projecting. He’s possibly even hoping.

Because Thomas, entering his third season, has 256 NFL carries and has averaged only 3.5 yards per carry in that time. Miller, meanwhile, has only 51 NFL carries, so we don’t know what he is for sure.

Yes, Thomas is big (6-1) and burly (235 pounds) and can hammer inside or slide outside with ease. And Miller is fast (4.4) and has a good college pedigree.

But Thomas is nonetheless known mostly for his fumbles and injuries the past two years, while Miller is known for his college days that mean nothing in the pros.

The point is both these players have to emerge before they can be labeled — good or otherwise.

“I’m just trying to get better out here every day and trying to have it carry it over to the regular season,” Thomas said. “I’m trying to improve my pass protection and holding on to the ball. Those are the main two things. Everything else will fall in place once we get rolling.”

Miller, who confidently predicted before training camp he could rush for 1,500 yards this season, might still do just that. But he has yet to separate from Thomas and, in truth, has failed to win a job that was presumed to be his.

That’s a disappointment at this stage.

This job was Miller’s to lose. And he’s slowly doing just that. He has left the door open for Thomas and what didn’t seem like much of a competition at the beginning of camp has turned into one.

Miller has started every exhibition game and until Tuesday was taking a majority of the first-team snaps. But he had that fumble in the preseason opener and last Saturday against Houston dropped a pass on third down that caught Philbin’s attention.

“Obviously, Lamar has to catch the ball on third-and-2 when you’re wide open like that,” Philbin said. “That’s a play you have to make in that critical situation early in the ballgame. You want to start fast. I mean, they’ve both had a productive camp, [but] there are still plays to be made before the final decision.”

The good news is the final decision doesn’t necessarily have to come right away. Yes, it would be nice if either Miller or Thomas would claim to the job coming out of Saturday’s preseason game.

But if neither does that, the competition can probably continue the following week without disrupting anything because the Dolphins plan to use both players in the regular season regardless of which one takes the first snap from scrimmage.

Despite this apparent luxury, however, the question of which player actually starts is an important one for the parties involved.

It matters to the players …

“I mean, it does,” Thomas said. “Every guy wants to be that guy, the No. 1 guy. So it does.”

And it matters to Philbin …

“We want to reward the guys we feel earned positions on the football team,” he said. “So, obviously, it’s going to be important who the starter is.”